Elevator control system



Oct. 26, 1948. G, WATSON HAL 2,452,342

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Filed June 24, 1944 Patented bot. 2.6, 1 948 ELEVATOR CONTROL SYSTEM Gavin Watson, Ossining, and William Henry Bruns, Lincolndale, N. Y and Harold Edward Galanty, Hillside, N. J assignors to Otis .Elevator Company, New York, N. 51., a corporation of New Jersey Application June 24, 1944, Serial No. 541,970

42 Claims. 1

The invention relates to elevator systems.

The object of the invention is to cause operation of theelevators so as to obviate undue waiting by intending passengers for response to calls.

The invention is useful in elevator control systerns in which the starting of the elevator car after, each stop is under the control of an attendant in the car, while the stopping of the car is automatic, stops to discharge passengers being made in response to push buttons within the elevator car operated by the attendant as directed by the passengers, and stops to take on passengers being made in response to push buttons at the landings operated by the intending passengers themselves. At intermediate landings, two push buttons are provided, one an up button for operation by intending passengers desiring to be carried in the rip-direction and the other a down button for operation by intending passengers desiring to be carried in the down direction. With such control applied to a plurality of elevator cars, push buttons at the landings are common to the cars.

In such installations, it often happens during busy periods that cars which are filled to capacity are non-stopped past floors for which calls have been registered from the floors with the result that the intending passengers who registered such calls have lengthy waits before getting service, This is especially true during peak demand periods of'the day which occur in the morning when the building is being filled, the evening when it'isbeing depopulated and at noon when there is heavy traffi both outgoing and incoming. During the evening peak for example, in-

tending passengers at intermediate and lower floors who have registered down calls may have to wait for considerable periods for response owing to the cars being filled to capacity at floors above, necessitating non-stop operation.

The invention involves giving preference with respect to hall calls to those which have been registered for more than a certain length of time. The invention will be described as applied to an elevator system in such way as to give preference to down calls which have been registered for such time periods.

In carrying out the invention for such application, upon the expiration of a predetermined time interval after the registration of an unanswered down call, this call becomes effective to stop an up travelling car and set it for travel in the down direction. However, it is preferred to stop a car which has no push button within the car pressed for a higher floor and such car will hereinafter be referred to as an available car.

Various installations have different trafiic problems and it may be considered desirable when more than one of such timed calls exist, to give preference to the lowest, the highest or the longest of such calls, depending upon the requirements of the particular installation. In the case of the lowest of such calls, the first available car set for upward travel to reach a floor for which a down call has been registered for more than a certain length of time is caused to stop at that fioor even though down call which also have been registered for more than such time exist for floors above. In the case of the highest of such cells, where two or more down calls have been registered for more than a certain period of time, the first available car set for upward travel to reach the highest of the floors for which such calls then exist is caused to stop at that floor and the other of such calls are not responded to as timed calls until after such highest call has been picked up. In the case of the longest of such calls, where two or more down calls have been registered for more than a certain length of time, only the longest of these is effective as a timed call, and upon that call being responded to the next longest becomes effective as a timed call.

Any of these timed calls may be answered by cars in the regular course of operation. In each case in which a car stops at a floor in response to a timed call, it is set for travel in the down direction. Thus upon being started, it travels in the down direction stopping to pick up down calls for floors below until filled to capacity. In the embodiments of the invention illustrated, the system may be changed over to provide any of these operations.

Features and advantages of the invention will become apparent from the following description and appended claims.

In the drawings:

Figure 1 is a simplified schematic representation of an elevator installation in accordance with the invention;

Figures 2a and 2b, taken together, constitute as simple and direct as possible.

3 a simplified Wiring diagram of the push button control circuits, the call pick up and call restoring circuits and the timing circuits for a plurality of elevators in accordance with the invention;

Figure 3 is a simplified wiring diagram of the power and control circuits for one of these elevators;

Figure 4 is a simplified wiring diagram of anbther arrangement of circuits for controlling the operation of the elevator cars in response to the timing apparatus; and

Figures 2s, 3s and 4s are key sheets for Figures 2a and 22), Figure 3 and Figure 4 respectively, showing the electromagnetic switches in spindle form with the contacts and coils on the spindles in horizontal alignment with the corresponding contacts and coils on the wiring diagrams.

For a general understanding of the invention, reference may be had to Figure 1, wherein various parts of the system chosen to illustrate the prinoiples of the invention are indicated by legend. Two elevators are illustrated, the arrangement being the same for each elevator. Each car is raised and lowered by means of a hoisting motor,

which motor. drives a traction sheave over which pass hoisting ropes for the car and counterweight. An electromechanical brake is provided and is applied to effect the final stopping operation and to hold the car when at rest.

Each elevator car is provided with a car operating panel on which are located a plurality of control switches for operation by the car attendant. These switches include a start control switch, a plurality of push buttons, one for each floor above the lower terminal, hereinafter termed car buttons, a safetyqswitch and a non-stop button. These switches are shown in the wiring diagrams of Figures 2a and 3.

' At each floor is a push button box within which are arranged push buttons, an up and a down push button at each intermediate floor and one push button at each terminal floor. These push buttons, which will hereinafter be termed hall buttons, are common to the cars.

In Figures 2a, 2b and 4 the circuits are shown for two elevators, as indicative of such circuits for any number of elevators controlled as a group. The circuits in all these figures are indicated for a seven floor installation. Figure 3 shows the starting. and stopping circuits and power circuits for one elevator, it being understood that such circuits are provided also for the other elevators.

The circuits of Figures 2a, 2b, 3 and 4 are shown separated in such manner as to render the circuits The relationship of these coils and contacts may be seen from Figures 28, 3s and 4s, where the switches are arranged in alphabetical order and shown in spindle form. The positions of these coils and contacts in the wiring diagram may be found by referring to Figures 23, 3s and 4s, where the coils and contacts are positioned on the spindles in horizontal alignment with the corresponding elements of the wiring diagram.

The control system illustrated has been considerably simplified. Such system has been shown because it facilitates disclosure of an application of the invention. It is to be under-stood that other control elements and safety elements may be added in making up the system and that such system is subject to many variations. For example, the invention may be applied to the control system disclosed in the patent to Waters and Glaser No. 2,074,575, dated March 23, 193i.

Before discussing the timing apparatus, the circuits and mechanisms of Figure 2a and 3 and certain operations of the elevators will first be described.

The electromagnetic switches employed in the circuits illustrated in Figures 2a and 3 are designated as follows:

ASMAuxiliary stopping switch BK-Brake resistance relay BRBrake E-Speed switch EA-Auxiliary speed relay II--Field and. brake switch NS-Non-stop relay OS-Operating switch sequence relay PDDown direction switch PR-Auxiliary direction relay PUUp direction switch SlVI-Stopping magnet XCHighest car call relay Xl-I--Automatic return relay XSHighest hall call relay Throughout the description which follows, these letters will be applied to the coils of the above designated switches. Also, with reference numerals appended thereto, they will be applied to the contacts of these switches. Difierentiation will be made between the different elevators by appending in Figure 2a to the characters employed to designate the various elements of the control system numbers indicative of the difierent elevators and arranged in brackets.

The up hall buttons are designated U, while the down hall buttons are designated D. Numerals are appended to these letters indicating the floors for which the buttons are provided, the letter T being appended to the down button at the top floor instead of a number. The hall buttons act through electromagnetic floor relays designated first by the numeral corresponding to the floor for which the floor relay is provided and then by the letter U or D in accordance with whether the floor relay is for an up hall button or a down hall button. Each floor relay, once operated, is retained in operated condition until the registered call is answered. Each floor relay is illustrated as provided with an operating coil and a restoring coil, being latched either mechanically or electromagnetically in operated condition upon energization of the operating coil and reset upon energization of the restoring coil. The car buttons are designated C and, as in the case of the hall buttons, have numerals appended thereto as indicative of the floor for which the car buttons are provided. Each elevator has a car button for each fioor abovethe lower terminal floor. Each elevator also has a non-stop button in the car, designated NSB. As in the case of the electromagnetic switches, differentiation is had between the car buttons and non-stop buttons for diiferent elevators by appending to these characters numbers in brackets. The electromagnetic switches are illustrated in deenergized condition, direction switches PU and PD, which are of the latching type, being shown in reset condition,

Mechanism actuated in accordance with movement of the elevator car is utilized in the control circuits of each elevator. Such mechanism may be in the form of a floor controller or selector machine as indicated in Figure 1 and it will be assumed that the mechanism is of the construction shown in the aforementioned patent to Waters and Glasser No. 2,074,575. Details of this mechcarriage of the selector for that elevator. brushes are arranged to cooperate with stationanism are not shown as such details are given in the Waters and Glaser patent, to which reference maybe made.

Each selector machine is driven preferably means of a tape attached to the car and counterweight and having teeth formc-dthereon for engaging teeth on .the selector driving wheel, as set forth in the patent to David Carl Larson No. 2,306,816, granted December 29, 1942.

Each selector machine comprises a crosshead which is driven by a screw, which in turn driven by a chain and sprocket in turn driven from the shaft upon which. the driving Wheel is mounted, to move in accordance with movement of the car for which the machine is provided. The crosshead carries a carriage upon which is mounted mechanism for controlling circuits to cause the car to be slowed down and stopped at a floor. Mechanism is also mounted on the carriage for causing slow down to begin at a certain distance n from the floor and for causing the car to be brought to a stop as it arrives at the floor. The carriage is advanced from a neutral position with respect to the crosshead in starting the car and is brought to a stop after a. certain amount of move ment. Thereafter the carriage moves with the crosshead. When circuits are set up to cause the car to be slowed down, the carriage i brought to a stop. The crosshead, which moves with the car, thereafter takes up the advance of the carriage so that when the car comes to a stop, the carria e is again in neutral. This relative motion of the carriage and crosshead is utilized to control the slow down and stopping of the car.

The advance of the carriage is effected by means of a torque motor which will hereinafter be termed the advancer motor. She circuits of this motor appear in Figure 3 where the motor is designated AM. Energization of the a-dvancer motor is controlled by contacts operated by the stopping magnet. The circuits of this magnet appear in Figures 2a and 3 where the magnet is designated SM. The magnet controls the extension and retraction of pawls carried by the carriage for cooperation with stopping lugs. A stopping lug is provided for each floor'and is arranged on a floor bar, these floor bars being spaced in accordance with the distance between the floors for which the lugs are provided. The stopping magnet is energized in the starting operation to effect the rethe floor for which the call is registered. The

pawl for the direction in which the car is travelling engages the stopping lug, bringing the carriage to a stop. The crosshead continues its upward movement and, due to the relative movement between thecrosshead and the carriage, effects the opening of selector switches SS2 and SS! in sequence to effect the slow down and stopping of the car.

The travelling brushes for each elevator illustrated inFigure 2a are carried by a panel on the These ary contacts for the various floors mounted on the floor bars. When the car is stopped at a floor, the brushes are in engagement with their cooperating stationary contacts for that floor. Being on the advance panel, however, these brushes are advanced in starting the car, are latched in engagement with their contacts for a floor by the pawls when a call is picked up and are maintained in that condition as the advance is taken up as the car comes into the floor.

As in the case of the electromagnetic switches, differentiation between the corresponding elements of the selectors for the different elevators in Figure 2a is made by appending numbers in brackets to the characters employed for these elements. tationary contacts subject to the car buttons are designated 33, 3 1, and 35 for floors 2, 3, e, 5 and 6 respectively, the stationary contacts 3! and 3'! for the first and seventh floors being connected directly to the feed line. These contacts are engaged by brush 38. Instead of providing brushes and contacts for the hall call restoring circuits separate from those for the hall call pick up circuits, as is disclosed in the aforementioned Waters and Glaser patent, for convenience the same contacts and brushes are used for both circuits with a switching arrangement to insure the desired sequence of operation. It is to be understood, however. that the same arrangement as disclosed in the Waters and Glaser patent may be employed. The stationary contacts subject to the down hall. buttons the second, third, fourth, fifth, sixth and seventh floors and the stationary contact for the first floor in the call pick up and call restoring circuits are designated 41, 42, Q3, 44, e5, 16 and ii for the first, second, third, fourth, fifth, sixth and seventh floors respectively. These contacts are engaged by brush 3. The stationary contacts subject to the up hall buttons at the i second, third, fourth, fifth and sixth floors and the stationary contact for the seventh floor in the call pick up and call restoring circuits are designatedfii, 52, 53, 55, 55 and 5? for the first, second, third, fourth fifth, sixth and seventh floors respectively. hese contacts are engaged by brush 58. Static-nary contacts 61,52, 53, 64, 65 and 58 for the first, second, third, fourth, fifth and sixth floors respectively are arranged in the highest hall call circuits to be engaged by brush 58.

Each selector has a plurality of hook switches 82, 83, 84, and 86, one for each of floors 2, 3, 4, 5 and 5, mounted on the floor bars for these floors to be engaged by a travelling cam 88 of insulating material also carried by the advancer panel. This cam is of a length to engage and open the hook switch for any particular fioor slightly ahead of the engagement of the call pick up brushes with the stationary contacts for that floor when the car is travelling in the up direction and to engage and open the hook switch for the floor below such floor slightly ahead of the engagement of the call pick up brushes with the stationary contacts for such floor when the car is travelling in the down direction. Also, brush 53 in the highest hall call circuit is of a length to engage its stationary contacts slightly ahead of the engagement of the call pick up brushes with their contacts for the corresponding floors when the car is travelling in the up direction. The travelling crosshead of each elevator also carries an additional brush 98 (see Figure 3) for engaging stationary contacts 9i and 92 for the terminal floors. This brush is not advanced with the carriage but moves directly with the crosshead. This has to do with controlling the operation of direction switches PU and PD. An additional hook switch I22 (see Figure 3) is provided on the selector machine.

ignated 96 and its series field winding Bl.

This switch may be arranged to be operated by cam 88-) so as to be open when the car is at the first floor and closed when it leaves the first floor. For convenience, however, a separate cam I23 (arranged. on the advancer panel) is illustrated for operating this switch.

Any suitable form of power supply may be provided for the elevator motor. One of the preferred arrangements is to employ a direct current elevator motor and to cause current to be supplied to the motor at a variable voltage, as from a, driven generator in accordance with Ward- Leonard principles. Such arrangement is illustrated in Figure 3 and motor generator sets are shown in Figure 1. It is to be understood that either a direct current or an alternating current motor ma be employed to drive the enerator, depending upon the kind of power supplied to the building and the character of the installation, and that any suitable control arrangement there- 'for may be utilized, such, for example, as one embodying the principles of the arrangement disclosed in the patent to Lindquist, Waters and Glaser No. 1,997,260, granted April 9, 1935.

When the generator is driven by an alternating current driving motor, an exciter which may be driven by the driving motor is employed to supply current to the separately excited field windings of the supply generator and the elevator motor and to the brake and the coils of the various electromagnetic switches of Figure 3. In such arrangement, the supply lines of Figure 3 would be connected to the exciter. Also, the call pick up and call restoring circuits and highest call cirsuits for each elevator would be connected to the respective exciters. The hall button circuits through the operating coils of the floor relays, however, would be subject to the source of supply .for the building so as to permit the operation of the floor relays at any time.

The armature of the generator is designated 95, the separately excited field winding being des- The armature of the elevator motor is designated 93 and its separatel excited field winging I00. A resistance llll is provided for controlling the strength of the generator separately excited field and therefore the voltage applied to the elevator 7 M12 is a discharge resistance for the brake release coil BR, while resistance motor armature.

)3 serves as a cooling resistance for this coil.

The contacts operated by the car gate and engaged when the gate is closed are designated G.

The door contacts operated by the various doors are arranged in series relation. These contacts are not closed until the doors are closed and locked. For convenience these door contacts are shown as a single pair of contacts designated DL. The car gate and hatchway doors for each elevator have not been shown but it is to be understood that they may be power operated, for example as disclosed in the aforementioned patent to Waters and Glaser No. 2,074,575. The start control switch in the car has a pluralit of contacts designated W5, W6 and IE7. H is the safety switch in the car. I26 are service switches for the respective elevators. It will be assumed that the service switches are in the positions illustrated.

The control system is illustrated for the condition where the cars are standing at the first floor. To facilitate understanding of the system, the starting and stopping of car No. 1 will first be described. Assume now that the power is applied to the system. This completes the circuit for the coil of elevator No. 1 non-stop relay NSC) through elevator No. 1 non-stop button NSBH). Relay NS(!) upon operation engages contacts NSHD. Contacts NSIU) control the circuits for the brushes 48(l) and SSH) in elevator No. 1 call pick-up and call restoring circuits. The application of power to the system also results in energization of elevator motor field winding I00.

When car No. 1 last arrived at the first floor, brush 9B engaged stationary contact 92 and, upon the engagement of contacts H! in the stopping operation, a circuit was established for the reset coil of down direction switch PD and for the operating coil of up direction switch PU. This caused the down direction switch to be reset, the condition in which it is shown in the drawings, and the operation of switch PU and latching of this switch in operated condition. The operation of switch PU caused the engagement of contacts PUHI), PU2, PU3, PU4, PU6, PUT, PU8, PU9 and PUlfl and the separation of contacts PU5. Contacts PUl l) are in the circuit to brush 68( I) so that the engagement of these contacts completcs the circuit for the coil of highest down hall call relay XSH) through the #2 contacts of the floor relays in series (TDZ, etc.) contact Bl (I brush 68M) and contacts FUN!) and XCIU). Contacts PU2 are in the circuit for the coil of automatic return relay XH. Contacts PU3 are in the circuit for the coil of auxiliary direction relay PR. Thus, upon the application of power to the system, auxiliary direction switch PR is operated. Contacts PU4 are in the circuit for car button magnet CBM so that this magnet is energized as a result of application of power to the rest of the system. Contacts PU5 disconnect the operating coil of up direction switch PU and the reset coil of down direction switch PD from the feed lines. Contacts PUB connect field winding AM i25 and armature AM 526 of the advancer motor in parallel. Contacts PU! control the circuit for the coil of brake and field switch H and contacts PUB control the circuit for the coil of speed switch E. Contacts PU9 and FUN) prepare the circuit for the generator separately excited field Winding 98 for upward travel of the elevator car.

Auxiliary direction relay PR upon operation separates contacts PRHI) and engages contacts PRZH). The separation of contacts PRHI) renders down hall call brush 48(1) ineffective for up car travel, while the engagement of contacts PRZH) renders the up hall call brush 58H) effective for up car travel.

To start the car, the start control switch is thrown to full running position. This causes the bridging of contacts me, $06 and I01, contacts I86 being bridged ahead of contacts '35 and Hill. The bridging of contacts we completes circuits (not shown) causing the closing of the car gate and first floor hatchway door. It also completes a circuit for the operating coil of stopping magnet SM through contacts 0st and EAA. The stopping magnet upon operation engages contacts SMHI), SM2 and 8M3. Contacts SMHI) are in the circuit for the neutralizing coil SMH) of the stopping magnet. Contacts SM3 complete a holding circuit for the operating coil of the stopping magnet. Contacts SMZ complete a circuit for the coil of auxiliary stopping switch ASM and for one coil of auxiliary speed relay EA. Relay EA does not operate at this time. Switch ASM operates to separate contacts ASMZU) and to engage contacts ASMHI), ASM3 and ASMQ. Contacts ASM2(I) are in a by-pass circuit for the neutralizing coil SMH') of the stopping magnet. Contacts ASMS are in the circuit for the coil of automatic return relay XH. Contacts ASMI(I) are in the circuit from brush 38H) to coil SM(I). Contacts ASMA prepare the circuit for the advancer motor AM, which is completed by the bridging of start control switch contacts- Iii5, this circuit being through field winding AMIZ? and through field winding AMI25 and armature AMi26 in parallel. This results in the operation of the advancer motor to advance the carriage in the up direction. The advancer motor also eifects the engagement of selector switches SSE and SS2, preparing the circuits for the coils of field and brake switch H and speed switch E and completing the circuit for a second coil of auxiliary speed relay EA.

The energization of both coils of relay EA causes this relay to operate to engage contacts EAHI) and EA2 and to separate contacts EA3 and EA4. Contacts EAI (I) are in the circuit for the neutralizing coil SMH) of the stopping magnet, the advance having progressed sufiiciently by this time for the brushes to be off the stationary contacts for the floor at which the car is positioned. Contacts EAZ further prepare the circuit for the coil of automatic return relay XH. The separation of contacts EA3 prevents energization of the direction switches once the advancer mechanism has been energized to advance the carriage. Contacts EA4 prevent reoperation of the stopping magnet once a call has been picked up after the car has come to a stop at the floor for which the call is registered. This is especially useful in cases where the advancer mechanism advances the brushes into engagement with their stationary contacts for the floor beyond before starting of the car takes places, as, for example, in the system of the Waters and Glaser patent previously referred to.

The advance takes place fairly rapidly so that, upon the closure of the hatchway door and car gate, a circuit is established for the coil of field and brake switch H through contacts SSi, PUl, up limit switch I68, gate contacts G, door contacts DL, start control switch contacts I01 and safety switch I I0.

Switch H upon operation engages contacts H2, H3. H4, H5, H6, H7, H8 and H9 and separates contacts HI and HI B. The separation of contacts HI prevents operation of the direction switches during operation of the car. Contacts H2 bypass start control switch contacts I05 in the advancer motor circuit. Contacts H3 complete the circuit for the coil of operating switch sequence relay OS. The operation of operating switch sequence relay OS causes the engagement of contacts OS2 and sepaartes contacts O'SI. The purpose of contacts OS! will be explained later. The engagement of contacts CS2 completes a holding circuit for the coil of auxiliary stopping relay ASM. Contacts H4 by-pa-ss start control switch contacts IO'I, establishing a self-holding circuit for the coil of switch H. Thus with its contacts all by-passed, the start control switch may be returned to off position. Contacts H5 further prepare the circuit for the coil of speed switch E.

Contacts H5 and H1 complete the circuit for brake release coil BR, while contacts H8 and H9 complete the circuit for the generator field winding 96. Contacts HIB disconnect the generator field winding from across the generator armature. The

completion of the circuit for the generator separately excited field winding causes current to be supplied from the generaor armature 95 to the hoisting motor armature 98 and, the brake being released as a result of the energization of its release coil BR, the elevator motor starts the car in the up direction.

The brake, upon being released, effects the separation of contacts BRI, which act to remove the short circuit for the coil of brake resistance relay BK. This relay operates to separate its contacts BKZ to insert cooling resistance I03 in circult with brake release coil BR. It also engages contacts BKI, which completes the circuit for the coil of speed switch E through contacts H5, SS2, PUS, up limit switch III and safety switch IIO. Switch E upon operation engages contacts EI' to short circuit a portion of resistance IIII in the circuit of the generator field winding 96. This applies full voltage to the generator separately excited field winding, causing the enerator voltage to build up to full. value to bring the elevator car up to full speed.

Assume that before the start control switch for car No. l was thrown to running position to start the car, an intending passenger at the third floor pressed the up third floor hall button U3. This caused energization of the operating coil of up third floor relay 3U. This relay upon operation engages contacts 313! and separates contacts 3U2' and is retained in operated condition. The engagement of contacts SUI renders stationary contact 53 alive. The separation of contacts 3U2 breaks the circuit for the coils of highest hall call relays XS. When brush 58( I) engages con tacts 53(I) a circuit is completed from line through restoring coil 3U and contacts 3UI of the up third floor relay, third floor stationary contact 53G), brush 58(I), contacts PRZH) and NSI (I), neutralizing coil SM( I.) and. contacts EA! (I) and SMI (I to line The neutralizing coil acts to oppose the operating coil of stopping magnet SM, releasing the pawl andcausing the separation of contacts SMI (I) 8M2 and SM3. Contacts SMI (I) and SM3 break the energizing circuits for the coils of the stopping magnet, while contacts SMZ break the circuit for the coil of the auxiliary Stopping switch ASM and one coil of auxiliary speed relay EA. The auxiliary stopping switch separates contacts ASMI(I), ASM3 and ASM l and reengages contacts ASM2(I). Contacts ASMIU) disconnect brush 38(I) from line Contacts ASMZ short circuit neutralizing coil SMH) of the stopping magnet. This increasesthe current supplied to the restoring coil of the up third floor relay 3U, causing this relay to be reset. This permits the reestablishment of the circuit for the coils of highest hall call relays XS. The operation of relay XSM) to engage contacts XSl, however, does not cause the operation of automatic return relay XH because contacts ASM3 are now separated. Contacts ASM4 deenergi-Ze the advancer motor AM. Relay EA does not drop out on deenergization of its coil in series with the.

' coil of switch ASM, being held in operated condition by its coil in parallel with the coil of speed switch E.

As the car continues its upward travel the up pawl, engaging the third floor stopping collar, causes the opening of selector switches SS2 and SSl in sequence. The opening of switch SS2 breaks the circuit for the coil of speed switch E, which drops out, separating contacts El to reinsert resistance MI in the circuit of the generator separately excited field winding. This decreases the voltage of the generator, causing the car to slow down. The opening of switch SS2 also breaks the circuit for the other coil of relay EA, which drops out to separate contacts EA! l) and EA2 and to reengage contacts EA3 and EA l. Contacts EAIH) are in the circuit for the neutralizing coil of the stopping magnet already broken at contacts SMHI). Contacts EAZ are in the circut for the coil of relay XH, already broken at contacts ASM3. Contacts EA3 further prepare the circuit for the operating coil of down direction switch PD and the reset coil of up direction switch PU. Contacts EA4 are in the initial energizing circuit for the operating coil of stopping magnet SM, thi circuit being open at contacts OSIU).

The opening of switch SSI, which occurs as the car arrives at the landing, breaks the circuit for the coil of field and brake switch H. Switch H, upon dropping out, separates contacts H2, H3, H4, H5, H6, Hl, H 8 and H9 and reengages contacts HI and Hlil. Contacts H2 are in the circuit for the advancer motor AM, which was previously deenergized. Contacts H3, H4 and H5 are in the circuits for the operating coils of magnet SM and switches H and E, which circuits have already been broken. The separation of contacts H6 and H! deenergizes brake release coil BR and the separation of contacts H8 and H9 disconnects the generator separately excited field winding 95 from the feed lines. Thus the external excitation of the generator is discontinued and the brake is applied to bring the car to a stop at the third fioor landing. The engagement of contacts HID reconnects the separately excited field winding across the generator armature substantially to destroy the residual flux of the generator field.

The separation of contacts H6 and H1 also breaks the circuit for the coil of brake resistance relay BK which drops out to separate contacts BKI and reengage contacts BK2. Contacts BK! are in the circuit for the coil of speed switch E, which circuit has already been broken. Contacts BKZ short circuit cooling resistance I63 for the brake release coil in preparation for the next starting operation. The separation of contacts H3 also breaks the circuit for the coil of operating switch sequence relay OS, provided the start control switch has been returned to neutral position. However, if the start control switch is held in position where contacts IE6 are bridged, relay OS remains energized upon the separation of contacts H3 so that contacts OS! remain separated to prevent the reopenation of stopping magnet SM. This prevents a restarting operation unless the start control switch is returned to neutral.

Assume that a passenger enters the car at the third floor desiring to be carried to the fifth floor. Upon the passenger announcing his destination, the attendant presses car button 05(8) which is held in operated condition by magnet CBM. This button not only renders stationary contacts 35(1) alive but also completes a circuit through hookswitches 85( I) and 86( I) for the coil of highest car call relay XCU). Relay X-CH), upon operation, separates contacts XCH) =causing the deener-gization of the coil of highest hall call relay XSH). Cam 88G) engages and opens hook switch 85(l) during advance of the carriage causing the deenergization of relay XC(I). Thus, upon the engagement of brush 68(l) with stationary contact 65H) the circuit is completed for the coil of highest hall call relay XSH). Relay XSH) engages contacts XS! completing the circuit for the coil of automatic return relay XH. Relay XH, upon operation, engages contacts XHZ to become self-holding and engages contacts XHHI) to complete a circuit for neutralizing coil SMU), this circuit also being completed by the engagement of brush 380) with stationary contacts 35(I). This causes reset of the stopping magnet, which in turn causes the car to be slowed down and brought to a stop at the fifth floor in the manner previously described.

Relay XI-I also engages contacts XH i so that upon the engagement of contacts H! as the car is brought to a stop at the fifth floor a circuit is completed for the operating coil of down direction switch UD' and reset coil of the up direction switch PU. This causes the reset of the up direction switch to separate contacts PUl l PU2, PU3, PUQ, PUB, PUT, PUB, PUB and PUifi and the reengagement of contacts PUB. The completion of this circuit also causes the operation and latching of the down direction switch to engage contacts PDQ, PD6, PDT, PD8, PDQ and PD) and to separate contacts PBS. The separation of contacts PU9 and PUH] and the engagement of contacts PDQ and PDHB change over the circuit for the generator field winding for downward car travel. The separation of contacts PUI (l) renders brush 68(3) ineffective for downward travel. The separation of contacts PU2 deenergizes the coil of automatic return relay XH and prevents operation of this relay during downward car travel. The separation of contacts PU3 deenergizes the coil of auxiliary direction relay PR which drops out to separate contacts PR2(I) and engage contacts PR! I) to render brush 48( I) efiective and brush 53H) inefiective for down car travel. The engagement of contacts PUB prepares the circuit for automatic reoperation of the direction switches to restore the circuits for upward car travel when the car reaches the lower terminal floor. The separation of contacts PU l and the engagement of contacts P134 causes the deenergization and reenergization of the car button magnet CBM, car button C5(l) being released in the transition. The separation of contacts PU8 and engagement of contacts PD8 change over the advancer motor circuits for advancing the carriage in the down direction. The separation of contacts PU? and the engagement of contacts PD? transfer the circuit for the coil of switch I-I so as to be subject to lower terminal limit switch H6 while the separation of contacts PU8 and the engagement of contacts PDB transfer the circuit for the coils of speed switch E and relay EA so as to be subject to lower terminal limit switch Ill.

Thus, with the car set for downward travel at the fifth floor, upon operation of the start control switch to stop the car, it is started in the down direction. It is believed that this operation will be understood from the description given of startingthe car in the up direction.

If the car is set for travel in the up direction and the only button pressed for a floor above the car at the time brush 68(4) engages contact 66(l) is the down hall button D6 at the sixth floor, the engagement of this brush and contact completes the circuit for the coil of relay XSH).

This relay operates as previously described to cause the operation of automatic return relay XH in turn to cause the car to be slowed down and brought to a stop at the sixth floor and to be set for downward travel as it is brought to a stop. Relay XH also separates contacts X313 to deenergize auxiliary direction rela PR. Relay PR separates contacts PRZU), rendering brush 58(i) ineffective. It also engages contacts PRIKI), rendering brush 48) effective. This completes a circuit through sixth floor stationary contact 15M) for the restoring coil of the down sixth floor relay 6D, causing this relay to be reset.

If the down sixth floor relay and the up sixth iioor relay are both operated, the separation of contacts B-UZ prevents the operation of highest hall callrelay XS I) and thus prevents the operation of automatic return relay XH to set the car for downward travel upon its being brought to a stop at the sixth floor. Furthermore, as relay XI-I is not operated, contacts XH3 remain separated, preventing the reset of the down floor relay for the sixth floor by the engagement of brush 4'8( l) with contact d6 i Once the car set for upward travel has set up circuits to cause the direction of car travel. to be changed to down upon the car being brou ht to a stop at a floor, that is, once the circuit for the coil of its automatic return relay XH has been completed, the registration of a call for a floor above that floor or of an up hall call for that floor after the establishment of this circuit is inefi'ective to prevent operation of the direction controlling switches to set the car for downward travel as it comes to a stop. This is due to the fact that automatic return relay XH, upon operation. becomes self holding. Any such call registered by a hall button remains operated under such conditions so that this call is ultimately responded. to.

It is believed that it will be seen from the above description that car No. 1, once started in the up. direction, continues to travel in the up direction until it reaches the floor for which the highest call, either car call or down. hall call or both, is registered, before reversal becomes effective. In case the highest call is an up hall call, the car remains set for upward travel in order that the intending passenger may be taken in the indicated direction. During its travel in the up direction, stops are made in response to calls registered by car buttons for floors intervening the lower terminal and its ultimate destination, and also in response to up hall calls for such intervening floors. The stops are made in the order of succession of floors, regardless of the order in which the calls are registered.

During downward travel of the car, stops are made in response to all car calls and down hall calls that are registered. Up hail calls, however, are answered only by anuptravelling car. It is believed that the stops in response to car buttons will be understood from the previous description inasmuch as when a car button is pressed it is maintained operated by the car button magnet CBM. so that, upon the engagement of brush 38(1) with the contact rendered alive by this button, the call is picked up and the car is caused to slow down and come to a stop at the floor. Similarly, each down hall button that is pressed operates a down floor relay that remains operated until the contact rendered alive thereby engaged by brush 48(i) to pick up the call. This causes the stopping magnet to drop out, the floor relay to be reset and the car to be slowed down and brought to a stop at the floor at which the button is located. The stops are made. in the ill) 14 order of succession of floors regardless of the order in which the calls are registered.

The operation of elevator No. 2 is the same as that of elevator No. 1, previously described. With both cars set for upward travel, each up hall call is answered by the car whose brush i8 is the first to engage its stationary contact for the floor for which the call is registered. The highest down call is answered by the first car Whose brush 68 engages its stationary contact for the floor for which the call is registered. If only one hall call remains to be responded to for a floor above the cars, upon its being picked up by one of the cars, the other is automatically caused to slow down and stop at the floor the stationary contact for which is next to be engaged by brush 68 for that car after the reset of the floor relay, or if in engagement with a contact at that time at the floor for which the contact is provided.

Instead of becoming set for down car travel at intermediate floors under conditions such as set forth above, each elevator may be caused" to run to the upper terminal before reversing. This may be effected by opening service switch 620 for that elevator, preventing the operation of relay XS. This prevents operation of relay XI-I, thus preventing the automatic setting of the car for downward travel until the engagement of brush 9!) with contact 85 as the car arrives at the upper terminal and contacts Hi reengage.

During either type of operation, it often happens that a car becomes filled to capacity so that it is unable to take on any more passengers until discharge of passengers has been efiected. Under these conditions, the attendant in that car presses his non-stop button NSB, deenergizing the non-stop relay NS for that car. This relay drops out to separate its contacts NSl rendering brushes 48 and 58 for that car ineffective to pick up calls. The car buttons for that car, however, are not affected by the non-stop button so that these buttons are responded to and stops are made to discharge passengers.

It sometimes happens that trams conditions are such that several cars may be non-stopped past hall calls wit-h the result that the intending passengers who registered these calls have to wait for undue lengths of time beofe getting service. This situation is likely to occur during peak periods such as incoming mornin and noon peaks and outgoing evening and noon peaks. The system is arranged to cause cars to give special response to hall calls which have been registered i or more than a certain length of time. To illustrate the principles of the invention, this provision has been made on y with respect to down hall calls. The circuits are arranged so that down calls which have remained unanswered for more than a certain time interval are responded to by cars set for upward travel which have no car buttons for higher floors pressed. In responding to such call, the is brought o a stop at the corresponding floor and is set for travel in the down direction. This ope-ration is effected by timing apparatus and circuits controlled thereby such as shown in Figure 22) or Figure 4.

Referring first to Figure 2b the selector machine for each elevator car has an additional column of contacts which are controlled by timing apparatus. These contacts are provided for the second, third, fourth, fifth and sixth floors and are designated i2, 13, "M, 15 and "55 respectively. These contacts are mounted on the fioor bars for the corresponding floors to be engaged by a travelling brush 18. This brush is carried by the advancer panel and is of a length and positioned the same as brush 68. Each elevator is provided with an additional electromagnetic switch designated YS and termed timed down hall call relay. The operation of relay YS for each car is controlled by the engagement of brush 78 for that car with its stationary contacts subject to the control of the timing apparatus. The operation of any relay YS causes the car for which it is provided to be brought to a stop at the floor for which the stationary contact engaged by brush E8 to cause this relay to operate is provided and to be set i or travel in the down direction. Differentiation as to elevators is made by appended numerals in brackets as in Figure 2a.

Certain parts of the timing apparatus are individual to the respective floors and certain parts are common to the floors. It is preferred to arrange most of the timing apparatus as a unit and to enclose it, as indicated by Y, to seal it against moisture and dirt and to shield it against extraneous electrostatic and electromagnetic efiects.

Certain features of the timing apparatus are the subject matter of the copending application of William Henry Bruns, filed June 24, 1944, Serial Number 541,971, since issued as Pat. #2,4 l5,4.5'7, while other features are the subject matte of the copending application of William Henry Bruns and Harold Edward Galanty, filed June 24, 1944, Serial Number 541,972, and since issued as Pat. #2,4-.33,424.

The circuits individual to the respective floors are the same for each floor. Referring for eX- ample to the circuits for the second floor, the time interval, after which the down call becomes effective to stop a car set for upward travel, is obtained by the discharge of a condenser designated 20. ER is a discharge resistance for the condenser. The condenser acts through an electronic tube ZCT, hereinafter referred to as a controlled tube. The circuits are particularly adapted for the utilization of a hot cathode controlled tube which is prevented from firing by a negative bias on the grid 2GB with respect to cathode 20A provided by the charge on condenser 20. However, other types of controlled tubes may be employed. The anode of the controlled tube is designated ZAN. ZSG is a shield grid which is connected to the cathode. However, tubes without shield grids may be employed. ZIT is a .two element tube arranged in the condenser charging circuit and will hereinafter be termed an isolating tube. 2R! is a current limiting resistance in the condenser charging circuit, the purpose of which will be seen as the description proceeds. 2R3 is a resistance in the circuit for the control grid ZGRQthe purpose of which will be seen from later description. An additional pair of contacts ZDS on the down second floor relay are provided in these circuits external to the unit Y. These contacts when closed complete an auxiliary discharge circuit for the condenser, this circuit also includin the isolating tube 2IT. Arranged for selective connection in the plate circuit of the controlled tube is a loading resistance 2R4 and the coil 2TB, of an auxiliary time relay. Connected across coil 2TB. is a condenser 202 and resistance 2R2, the purpose of which will be explained later. Contacts of the auxiliar time relay are designated ZTRl. 2T0 and 2T0! are three position throwover switches for selecting circuits for different operations. The contact arm of switch 2T0] is connected directly to stationary contacts 72 on the selector machine while the contact arm of switch 2T0 is connected to the anode of the controlled tube.

The corresponding elements of the individual circuits of the unit for the other floors are similarly designated, difierentiation being had as to floors by numerals corresponding to floor numbers which precede the designating letters. In the case of the auxiliary time relays, those for the floors above the second fioor are provided with additional contacts which, for example in the case of the third floor, are designated 3TR2.

As to the circuits common to the various floors, direct current voltage for the plate circuits of the controlled tubes ZCT to BCT inclusive is provided from the direct current supply lines of Figure 2a. TP is the primary winding of a transformer supplied externally of the unit from a source of alterating current designated AC. TSI T82, TS3 and TSQ are secondary windings of this transformer. Secondary windings T83 and T84 are for supplying alternating current to the full wave rectifier REC. This rectifier provides direct current for the charging of condensers 20 to 6C inclusive. Filter condenser C8 and load resistance R8 are connected in parallel across the output supply lines RE+ and RE from the rectifier. Transformer secondary winding TS2 is utilized to supply current to the heater elements of controlled tubes ZCT to GCT inclusive. For convenience, the heater elements and connections to this secondary winding are not shown.

Alternating current voltage is superimposed on the direct current voltage applied to the plate circuits oi the controlled tubes. This superimposed alternating current voltage is provided by transformer secondary winding TS! The value of this superimposed voltage with respect to the direct current voltage applied to the plate circuits is such as to cause the resultant voltage applied to the tubes to be negative for a fraction of a cycle. This provides positive voltage for a major portion of the cycle and yet enables the grid of each tube to retain control to shut oi? the tube. Combined alternating and direct current voltage is of advantage for the plate circuits in that it enables the use of standard direct current switches in the plate circuits. This is useful in applying the apparatus to existing elevator installations. However, alternating current voltage alone may be applied to the plate circuits. Alternating current voltage provided by transformer secondary winding TS! is also superimposed on the direct current voltage provided by condensers 2C to 60 inclusive in the control grid circuits of the corresponding controlled tubes. Condensers C3 and C4 and resistances R3 and R4 constitute a phase shift network for controlling the phase relationship of the superimposed alternating current grid voltage with respect to the plate voltage.

TC is a manually operable time control switch which is part of time control mechanism for the common control of the time interval for all floors. Resistances R! and R2 are part of the time control mechanism. This mechanism is external to unit Y and may be arranged at the elevator starters station, R? is a protective resistance for isolating tubes 2IT to BIT inclusive. Resistance R9 and condenser C9 are subject to throwover switch TO! and are eiiective only in the intermediate position of this switch. When rendered efiective, resistance R9 serves as a loading resistance for the cathodes of the controlled tubes, being on the cathode side in a wire common to the cathodes. Condenser C9 serves to delay the decrease in potential drop across resistance R9 when a controlled tube is shut off. 'I'hrowover switches TOl, 2T0 to 6T0 inclusive and 2T0i to 6T0] inclusive are operated as a unit. SEI and SE2 are service switches for connecting in the timing apparatus for operation. The purpose of resistance RH! and condenser CH! connected across the coil of switch YS will be explained later.

When power is applied to. lines and a charge is caused to be built up on condensers EC to SC inclusive to cause negative potential to be applied to the control grids of the controlled tubes suificient to block the tubes. This is effected by connecting each of the condensers in series with its discharge resistance across resistances R4 and R5. Resistances R4 and R5 in conjunction with resistance R6 constitute a potentiometer resistance connected from line through transformer secondary winding TSI to line As there is no alternating current voltage in secondary winding TSI due to switch SE2 being open, direct current voltage is applied to the condensers. The relative ohmic values of these resistances are such that suflicient voltage is applied to the condensers to build up sumcient charge to prevent the firing of any controlled tube, should a floor relay be operated when switches SE! and SE2 are closed, until sulficlent time has elapsed to heat up the cathodes. This prevents disintegration of the cathodes. The amount of voltage applied to the condensers is not sufilcient to cause break-down of the isolating tubes ZIT to BIT inclusive which are connected across the corresponding condensers through resistances 2B! to ER! inclusive respectively and resistances R8 and R1.

Upon the closing of service switches SEI and SE2 the timing apparatus is rendered efiective for operation. The closing of switch SEI short-circuits resistance R5 to super-impose the alternatnig current voltage from the phase shift network onto the condenser voltages. The closing of switch SE2 connects the primary winding TP of the transformer to the alternating current source. Secondary windings TS3 and TS E cause rectifier REC to apply direct current voltage to supply lines RE+ and RE-. The value of this voltage is sufiicient to cause break-down of isolating tubes ZIT to SIT inclusive to effect the further charging of the condensers and thus raise the negative potential of the grids with respect to the cathodes. Taking condenser 2C, for example, as the condenser charge builds up the potential drop across resistance ZRI decreases until it becomes zero whereupon the isolating tube oes out. The

condenser then starts to discharge by way of discharge resistance 2B and resistance until, due to the lowering of the condenser charge, the voltage applied to the isolating tube rises to a point sufilcient to break down this tube. This recharges the condenser to a value to cause the isolating tube to extinguish. This cycle of operation is continuously repeated and may be termed a discharge, recharge cycle.

Upon the closure of contacts 2B3, the auxiliary discharge circuit for the condenser is completed. This circuit is through resistance R'l. At the same time resistance ZR! is connected across lines 832+ and RE-. Regardless of the point on the condenser discharge, recharge cycle that this occurs the potential drop across the condenser is sufficient to cause the isolating tube to break The current flow is in a direction opposite to that for charging the condenser and, owing to the fact that resistance R'l'is of low ohmic value, the condenser-discharges immediately to the value gh ohmic value of resistance 2R, this discharge takes place slowly, the rate depending upon the value or" this resistance. Should the call registered by the down second floor relay be answered and therefore contacts 2B3 separate before the condenser has discharged sufiiciently to reduce the negative potential in the control grid to a point to unblock the tube, the condenser immediately recharges and continues its discharge, recharge cycles.

Assume that the call is not answered and contacts do not separate before the condenser has discharged sufiiciently to reduce the negative potential on grid ZGR with respect to cathode ZLCA to a point to unblock the tube. For convenience, assume that voltage is being applied at this time to the plate circuit of the tube. Thus when this point is reached, the tube fires during the positive portion of the next cycle of the voltage applied to the plate circuit of the tube and continues to conduct during this portion of each succeeding cycle. The phase relationship of the alternating current voltage superimposed on the condenser discharge voltage with respect to the voltage applied to the plate circuit of the tube is such as to cause the tube to conduct near the beginning of the positive portion of each cycle plate voltage. This arrangement causes the tube when it becomes conductive to pass current in. the plate circuit the maximum amount of time during each cycle. Upon the subsequent separation of the floor relay contacts, the condenser is recharged and, upon the potential of the grid becoming negative with respect to the cathode a certain amount, the tube is shut off.

In order that the above described operations may be more clearly understood, assume that the direct current voltage of lines and is volts, that the peak value of the alternating current voltage superimposed thereon by transformer secondary winding TSI is 141 volts, and that indirectly heated hot cathode controlled tubes having characteristics suitable for these voltages and which are conductive at a critical grid voltage of approximately 2 volts are utilized. Assume further that the potential across lines RE+ and RE is 180 volts With condenser G8 a 4 inicrofarad condenser and with the ohmic value of resistance R3 30,000 ohms and of resistance R! 1,000 ohms. Assume further that each of condensers 2G to EC inclusive is a 4 microfarad condenser, that each of resistances 2R to 6B inclusive is a 20 megohm resistance and that the characteristics of each of isolating tubes ZIT to 61']? inclusive are such that it breaks down at 85 volts and becomes extinguished at 60 volts. Assume also that each of resistances 2R! to SRI inclusive is a 30,000 ohm resistance and each of resistances 2R3 to 6R3 inclusive is a 10,000 ohm resistance. Assuming that the ohmic values of resistances R5 and R5 are 2 and 1 megohms respeotively, condensers 20 to 50 inclusive will be charged from lines and to '73 volts.

Upon the closure of switches SE! and SE2, alternating current voltage is superimposed on the direct current supply lines and and the oltage of lines RE+ and RE- breaks down the isolating tubes and further charges the condensers as above described. Referring again to the circuits for, the down second floor relay, upon the voltage drop of condenser EC reaching volts the voltage drop across isolating tube T falls to 60 volts and this tube goes out. The condenser then starts to discharge through resistance 2R. Due to the high ohmic value of this resistance the discharge takes place relatively slowly. Upon the voltage across the condenser falling to 95 volts the voltage across the isolating tube reaches 85 volts causing the tube to break down. As a result, the condenser immediately recharges whereupon the isolating tube goes out and the condenser discharges again. This discharge, recharge cycle is continuously repeated.

Assume now that contacts 2D3 are closed. This may occur at any time during any one of the condenser discharge, recharge cycles. The isolating tube is conducting during the recharge portion of a cycle and, if the engagement of contacts 2D3 occurs then, the condenser voltage reverses the direction of current flow in the isolating tube in effecting the condenser discharge by way of the auxiliary discharge circuit. The isolating tube is not conducting during the discharge portion of a cycle so that, should the engagement of contacts 2B3 occur then, the condenser voltage causes the isolating tube to break down to effect the condenser discharge by way of the auxiliary discharge circuit. In either case, owing to the fact that resistance R? is of low ohmic value, the potential drop across the condenser drops immediately to the extinction voltage of the isolating tube, namely 60 volts, whereupon the isolating tube goes out. From this point on the condenser discharges slowly into its discharge resistance ZR as before. Upon the separation of contacts 2B3, the condenser is recharged and the discharge, recharge cycles are resumed.

Inasmuch as, upon the engagement of contacts 2D3 the condenser voltage falls immediately to the extinction value of the isolating tube, namely 60 volts, a uniform starting point for the timing operation is had, and as the phase relationship of the superimposed alternating current grid voltage with respect to the plate voltage is such as to cause the tube to start to conduct near the beginning of the positive portion of each cycle of voltage applied to the plate circuit, uniform timing intervals are had.

When the controlled tube fires, the grid potential becomes positive with respect to the cathode and the negative charge on the condenser is reduced. The values of resistances 2R3 and 2B! are such as to enable, upon the separation of contacts 2B3, the recharging of the condenser to be eiiected with the result that the tube is shut oil when the grid potential becomes 2 volts negative with respect to the cathode. The condenser is recharged to 120 volts and resumes its discharge, recharge cycles. The operation of the timing circuits for each of the other floors is the same.

The length of each timing operation may be varied by varying the value of the phase shift voltage superimposed on the condenser voltage. This is effected by time control switch TC. The position of the time control switch determines the amount of resistance connected in parallel with the right hand portion of resistance R3. In the top position of the time control switch the switch is open, in the next lower position the parallel resistance is R! of a certainohmic value, in the next lower position the parallel resistance is R2 of a lower ohmic value, and in the lowermost is short circuited. The net result is to decrease the potential drop across the terminals of resistthe condenser.

ance R3 as the time control switch is moved from its uppermost to its lowermost position, thereby decreasing the value of the phase shift voltage superimposed on the condenser voltage. The lower the value of the phase shift voltage the longer the time interval before the controlled tube is put in condition to conduct. It has been found that, for the characteristics of the circuits and apparatus previousl assumed, as to the values of the resistances and condensers of the phase shift network, resistance R3 may be 1759 ohms with the portion to the left of the connection to the time control switch 450 ohms, resistance R4 5,000 ohms, condenser C3 1 microfarad and condenser Ct .25 microfarad. With resistance RI 1,000 ohms and R2 250 ohms, time intervals approximating 1 minute, 1.5 minutes, 2 minutes and 2.5 minutes are obtained in the consecutive positions respectively of the time control switch TC from top to bottom.

For the purposes of further description of operation assume that the throwover switches 'I'Ol, 2T0 to 6T0 inclusive and 2T0! to 6T0! inclusive are in uppermost position as illustrated. This connects the anodes ZAN to BAN inclusive of the controlled tubes with contacts 1?. to H6 inclusive respectively of the selector machines. So long as no controlled tube is in condition to fire none of these contacts are alive so that the engagement thereof by their respective brushes 18 does not cause operation of relays YS. However, when the potential of the grid of any tube reaches 2 volts negative with respect to the cathode, that tube is in condition to fire and upon the engagement of any one of the selector machine contacts for the floor for which this tube is provided by its brush 78 when the car for which this brush is provided is set for up travel and is available, the tube is fired and relay YS for that car is operated. This causes the down floor relay for that floor to be reset and the car to be slowed down and stopped at that floor and set for downward travel.

Assume for purposes of more detailed descrip tion that the down second floor relay is operated and has not been responded to within the time interval for which the timing apparatus is set. Assume further that the next available car set for upward travel whose brush '58 engages its contact i2 is car No. 1. Upon the engagement of brush 78H) with contact 520) a circuit is completed from line (Figure 2a) through contacts XCI (I) closed because no car call is registered for a floor above, contacts PUHI), cross connecting wire WU), through (Figure 2b) the coil of relay YSH), brush 13), contact 12H), throwover switch Z'IOl, anode ZAN and cathode 20A of controlled tube ZCT, throwover switch TOE service switch SEI, and transformer secondary winding TSI, to line This causes controlled tube ZCT to fire and thus causes the operation of relay YSH). Condenser CHM!) in parallel with the coil of relay YSH) is to obviate the effect of the inductance of the coil and thus retain the negative portion of the cycle of voltage applied to the controlled tube. Resistance RHJH) serves as a current limiting resistance for Relay YS( upon operation engages contacts YS! (Figure 3) causing the operation of automatic return relay XH to cause the car to be brought to a stop at the second floor and set for travel in the down direction, and the reset of the down second floor relay, in the manner previously described, The reset of thefloor relay as this timed call is pickedup prevents the stopping to line is not operated as contact 12) 'However,=upon the engagement of brush 118(1) with-stationary contact 14) relay YSH is op- 21 Mother cars in 'response to this'call, puts out controlled tube 'ZCT'and recharges condenser "26 for resumption of its discharge, recharge cycles.

"Stops at other floors in response to timed calls rby'cars'setfor upward tiavelare effected in a similar'manner. In each case the timed'call is responded to by the first available car set for upward travelinefiect to reach the floor for which such isregistered, i. e., to engage the stationary contact for that floor by its brush [8. In case there are timed calls for more than one floor which have not in effect been reached by an available up car with no other available car in position to respond to these calls as timed calls, such car answers the call for the lowest'of these floors. This is considered desirable operation to meet the traffic problems'of buildings in which such timed calls which remain unanswered for undue lengths of time are most likely to occur at the lower floors.

In some buildings traffic conditions might be such that it would be'considered preferable where two or more timed calls exist with only one available car in position to answer them to cause the car to answer the highest of such calls. This operation may be had in the arrangement illustrated 'downsecond floor relay 2D is "operated and has not been responded to Within the time interval for which the timing apparatus is set. As this time interval expires a circuit is completed from line through the coil of second floor auxiliary time relay 2TH, "throwover switch 2T0, through controlled tube ZCT, throwover switch TOI, service switch'SEi, transformer secondary windin TSi, Condenser 2G2 and resistance 2R2 in parallel with the coil of relay ZHR serve the same purpose as condenser CH) and resistance RIO. The completion of this circuit fi es the tube "and thus causes the immediate operation of this i auxiliary time relay which engages contacts ZTR! to render second floor stationary contacts 12 alive. Thereafter, upon the first engagement of a brush 18 for a car set for upward travel with its con tact '12; a circuit is completed for the coil of relay YSfor that car through throwover switch ZTOI,

Contacts'ZTRl and contacts 3TR2 to 6TR2 inclusive, to line This causes that car to be brought to a stop at the second'fioor and set for travel in the down direction and reset of the fourth'floor auxiliary time relay lTR also is operated. 'RelaydTR by the separation of contacts 4TR2 breaks the circuit from line to all selector stationary contacts for'floors below the fourth floor so thatnone of contacts 12 are eiTective to cause operation of any of the corresponding relays YS. Thus, assuming further that there is no car set for upward travel which in effect has not reached the fourth floor other than car No. 1 and that this car also has not'yet in effect reached the secon'dfloor. Upon the engagement of brush 18H) with stationary contact 12(l), relay YSG) is not alive.

grid.

erated causing the car to be brought to'a stop at the fourth floor and set for downward travel and the fourth floor down call. to be reset as the call is picked up. The reset of the timed fourth floor down call causes the recharging of condenser AC to restart the discharge, recharge cycles. As the potential of the grid of controlled tube 50T with respect to the cathode becomes 2 volts negative, the tube is shut off. This causes deenergization of relay 3TH which reengages contacts dTRZto r .connect stationary contacts "52 to line thus enabling .1 call at the second floor to be responded to as a timed call.

It may be considered desirable for certain installations to cause, where two or more calls exist which have rer" ed unan wered for more than a certain lengt of time, the one which has been registered the longest to be responded to as a timed call first. In other words, where a plurality of such unanl vc d calls exist, such calls areresponded to as t ed calls in the order in which the calls were ered. This operation may be had in the arrangem -..t illustrated by moving the throwover switches to intermediate position. This connects the anodes of the controlled tubes both to the loading re. corresponding thereto to the corresponding contacts on the selector machine. It also removes the shunt for resistance R8 and its parallel condenser C9 rendering them eiifecti e. Assuming each of loading resistances to inclusive is of an ohmic value of 20,@90 oh. -s, resistance R8 would be a 4,000 ohm resistance and condenser C9 a so microfarad condenser. W 1 a controlled tube becomes conducting, resistance Ri acts to delay the firing of any other tube until after the conducting tube is shut off. while conden er (39 acts to cause the next tube to fire to be the or g for which the floor relay has been operated lon est. In other words, when a plurality of floor 1 ye have been or become operated for the prescribed period, only one controlled tube can be conducuog at a time and the order in which they become conductive is the order in. which the floor relays were operated. Resistance RE} condenser C8 are connected in the common w leadi g from line to the cathodes of the con-tr ed tubes. Thus, when floor relay 0G1 cts for one floor have been in engagement for the l "escribed length of time to cause the correspon :ng controlled tube to conduct, current flows through cathode loading resistance This raises the potential of the cathodes of all controlled tubes to block all of such tubes except the one which has fired.

Assume, for example, that the first down call to be registered for a certain length of time is the down call for the second floor. As previously explained, at the e: lraticn of this time period, the negative bias on the control grid of tube ZCT is reduced, sufiiciently by the condenser discharge to enable the tube to fire. Inasmuch the 2AM of tube is connected through thr wover switch 2T0 and loading resist ance 21% to line the tube fires immediately. The anode is also connected through throwover switch Z'IOi to stationary contacts T2 of the selector machines so that the firing of the tube renders these contacts alive. Inasmuch as the plate circuit of tubeZCT is through cathode reflow in this circuit causes-a this resistance. As to each to SGT inclusive, this voltage drop the potent' l of the cathode in a pos t e :1 on with to the control This an effect is the increasing 23 the negative bias of the grid with respect to the cathode. This blocks tubes 3CT to ESCT inclusive so that should one or more down calls for floors three to six inclusive be registered, when the time interval expires for the tube controlled by each such down call, the tube does not fire so long as tube 2CT is conducting. For the voltage values and characteristics previously assumed, the voltage drop across resistance RH when a tube fires would be about 17 volts which means that the condensers for other tubes would have to discharge an additional 17 volts before the tubes controlled thereby could also fire. As this voltage difference exists in the range of condenser discharge where the voltage change is relatively slow, the delay in the firing of other tubes is more than ample to insure the answering of the call corresponding to the tube already conducting. As to controlled tube ZCT, when it fires it immediately drains timing condenser 2C as grid resistance 2R3 is of relatively low ohmic value. Thus, although the cathode potential of tube ZCT is raised in a positive direction, the grid potential is raised in a positive direction at the same time enabling this tube to continue to conduct.

When the down call at the second floor is answered, contacts 2B3 separate and condenser 20 is recharged, as previousl described, to shut ofi tube ZCT. If the time interval for another call has expired the lowering of the voltage across resistance R9, due to tube ZCT being shut ofi, causes the controlled tube for this next timed call to fire, rendering the corresponding stationary contacts of the selector machine alive and blocking the other tubes. At the time controlled tube ZCT is shut ofi should there be more than one down call registered, the time interval for each of which has expired, condenser C9 delays the lowering of the voltage drop across resistance R9 sufiiciently to insure the firing of only the controlled tube corresponding to the longest remaining timed call. The delay provided by condenser C9 assures ample time for this controlled tube to ionize and thus fire before the difierence in potential between cathode and grid of another tube can become low enough to cause that tube to fire. Thus, only one tube conducts at a time and the firing of the controlled tubes in the order in which unanswered timed calls were registered is assured.

It will be seen, therefore, that when a timed call exists, such call is picked up by an available car set for upward travel. The particular timed call which is responded to, in case the time interval for more than one unanswered timed call has expired, is dependent upon the position of the throwover switches. These timed calls are responded to even though untimed calls exist for floors above since the timed call renders the corresponding contacts of contacts 72 to 16 inclusive alive. Thus relay YS for a, car is able to operate to cause the car to be brought to a stop at a. floor in response to a timed call for that floor even though due to the separation of floor relay contacts for floors above in the series circuit through contacts 2B2 to TD2 inclusive, the operation of relay XS for that car is prevented. It will be understood from previous description that whenever a car is stopped at a floor in response to a timed call and is set for travel in the down direction, it stops on its downward trip in response to down calls for floors below. Also any timed down call may be picked up as an untimed call by a car in the regular course of operation. Whenever a call is picked up, either timing apparatus.

as a timed call or as an untimed one, the floor relay is reset so that the call ceases to exist either as a timed or untimed call. When such reset is efiected the corresponding selector contacts are no longer alive, enabling other cars to continue past the floor to respond to calls for floors above.

The arrangement by which the timing apparatus controls the operation of the elevator cars is subject to considerable variation. For example, instead of an additional column of stationary contacts 12 to is inclusive on each selector subject to the timing apparatus, the timing apparatus may be arranged to act through contacts 62 to B8 inclusive in which event relays YS are omitted and relays XS are utilized in responding to timed calls. Such an arrangement i illustrated in Figure a in which the control circuits for the coils of the XS relays are included. The circuits for controlling the potential of the control grids of the controlled tubes are the same in Figure 4 as in Figure 2b, the variation being in the circuits controlled by the tubes. The coils of auxiliary time relays TR are connected directly to the anodes of the corresponding controlled tubes. With this a-rrangement, resistance R9 would be of a smaller ohmic value than 4,000 ohms when the resistance of the coils of relays TB is less than 20,000 ohms. In such case condenser 09 would be of a larger capacity. Breaking contacts 3TR2 to BTRZ inclusive of auxiliary time relays 3TB to 6TB. inclusive are arranged in the circuit from line to the coils of the auxiliary time relays. The eifectiveness of these breaking contacts is controlled by throwover switches STOi to 5T0! inclusive. Thus, when these throwover switches are in position to render these contacts efiective, the operation of any one of the auxiliary time relays breaks the feed circuit for the coils of the auxiliary time relays for all floors below. Each of the auxiliary time relays is provided with an additional pair of contacts, 2TR3 to 5TRL inclusive. These contacts, along with making contacts ZTR! to BTRl inclusive of the auxiliary time relays, control the circuits for rendering stationary contacts 62 to 65 inclusive of the selector machines alive by the These circuits lead to an ungrounded negative line designated UG which is utilized to provide a higher voltage for operating relays XS under control of the timing apparatus than that for operating relays XS under control of the No. 2 contacts of the floor relays. Each of service switches 20 is arranged in shunt to a resistance R! i.

As before throwover switches TO! and 3T0l to ST-Ol inclusive are operated as a unit. With these throwover switches in the position illustrated, each timed call is respondedto by the next available car set for upward travel in efiect to reach the ficor for which such call is registered, as in the case of the circuits of Figure 2b with the throwover switches in the corresponding position. Assume, for example, that the down fourth floor relay is operated and has not been responded to within the time interval for which the timing apparatus is set. Upon the expiration of this time interval, tube iCT fires to cause the operation of auxiliary time relay iTR. This relay, upon operation, separates contacts lTRB and QTRZ and engages contacts lTRl. Contacts QTRZ are bypassed by throwover switch iTOl. The engagement of contact 4TB! connects stationary contact-s 54 to negative line UG, rendering these contacts alive. Contacts lTR3 disconnect the series circuit ot back contacts 2D2 to TDZ inclusive of the floor relays from selector contacts E i-to pre- 

